相对于CALayer，CAShapeLayer更加复杂一些。
CALayer和CAShapeLayer:
相同：
普通CALayer在被初始化时是需要给一个frame值的,这个frame值一般都与给定view的bounds值一致,它本身是有形状的,而且是矩形.
CAShapeLayer在初始化时也需要给一个frame值,但是,它本身没有形状,它的形状来源于你给定的一个path,然后它去取CGPath值,它与CALayer有着很大的区别
CAShapeLayer有着几点很重要:
- 它依附于一个给定的path,必须给与path,而且,即使path不完整也会自动首尾相接
- strokeStart以及strokeEnd代表着在这个path中所占用的百分比
- CAShapeLayer动画仅仅限于沿着边缘的动画效果,它实现不了填充效果
以下给出如何使用CAShapeLayer
1.用CAShapeLayer创建view的一个蒙版层。
// 创建一个view
UIView *showView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
[self.view addSubview:showView];
showView.backgroundColor = [UIColor redColor];
showView.alpha = 0.5;
// 创建一个shapeLayer
CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
CGMutablePathRef path = CGPathCreateMutable();
// 创建一个需要给showView蒙版的区域
CGRect shapeRect = CGRectMake(20,20,100,100);
CGPathAddRect(path, nil, shapeRect);
// 这里可以给view设置多个蒙版
CGPathAddRect(path, nil, CGRectMake(200,200,50,50));
// 给CAShapeLayer设置一个路径，即frame
maskLayer.path = path;
showView.layer.mask = maskLayer;// 设置蒙版
CGPathRelease(path);
2.用CAShapeLayer画一个动态的圆。
// 创建一个view
UIView *showView = [[UIView alloc] initWithFrame:CGRectMake(100, 100, 100, 100)];
[self.view addSubview:showView];
showView.backgroundColor = [UIColor redColor];
showView.alpha = 0.5;
// 贝塞尔曲线(创建一个圆)
UIBezierPath *path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(100/2.f, 100/2.f) radius:100/2.f startAngle:0 endAngle:M_PI * 2 clockwise:YES];
// 创建一个shapeLayer
CAShapeLayer *layer = [CAShapeLayer layer];
layer.frame = showView.bounds; // 与showView的frame一致
layer.strokeColor = [UIColor greenColor].CGColor; // 边缘线的颜色
layer.fillColor = [UIColor clearColor].CGColor; // 闭环填充的颜色
layer.lineCap = kCALineCapSquare; // 边缘线的类型
layer.path = path.CGPath; // 从贝塞尔曲线获取到形状
layer.lineWidth = 4.0f; // 线条宽度
layer.strokeStart = 0.0f;
layer.strokeEnd = 0.1f;
// 将layer添加进图层
[showView.layer addSublayer:layer];
// 3s后执行动画操作(直接赋值就能产生动画效果)
[[GCDQueue mainQueue] execute:^{
layer.speed = 0.1;
layer.strokeStart = 0.5;
layer.strokeEnd = 0.9f;
layer.lineWidth = 1.0f;
} afterDelay:NSEC_PER_SEC * 3];
// 给这个layer添加动画效果
CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
pathAnimation.duration = 1.0;
pathAnimation.fromValue = [NSNumber numberWithFloat:0.5f];
pathAnimation.toValue = [NSNumber numberWithFloat:0.8f];
[layer addAnimation:pathAnimation forKey:nil];
// 创建一个gradientLayer
CAGradientLayer *gradientLayer = [CAGradientLayer layer];
gradientLayer.frame = showView.bounds;
[gradientLayer setColors:[NSArray arrayWithObjects:(id)[[UIColor redColor] CGColor],(id)[[UIColor yellowColor] CGColor], nil]];
[gradientLayer setLocations:@[@0.5,@0.9,@1]];
[gradientLayer setStartPoint:CGPointMake(0.5, 1)];
[gradientLayer setEndPoint:CGPointMake(0.5, 0)];
